Effects of feeding rate on liver histology and immune function of Micropterus salmoides under land-based circular-pond recirculating aquaculture systems

Wei Yunyong; Wang Mengran; Liu Hongxiang; Shen Jiajia; Gao Feng; Cheng Guangping; Ma Yanqun

doi:10.20154/j.cnki.issn1672-9692.2025.08.010

Abstract：This study aimed to investigate the effects of different feeding rates on serum lipid levels,liver antioxidant capacity,immune function,and histology of Micropterus salmoides in a land-based circular-pond recirculating aquaculture systems,in order to determine the optimal feeding strategy.The experiment selected Micropterus salmoides with a body weight of(23.31±1.25)g as the research subjects and randomly divided them into four groups(1.5%group,2.5%group,3.5%group,and 4.5%group)according to the feeding rate.Two replicates were set in each group,and each replicate was raised in one experimental pool,with 3 660 bass(73 bass/m2)released in each pool.After 7 days of temporary rearing,30 bass were randomly selected from each pool to measure their body weight,and the average daily feeding amount for each group was calculated.The test period is 60 days.The results showed that compared with the 1.5%and 2.5%groups,a feeding rate of 4.5%could significantly increase the contents of serum triglycerides(TG)and total cholesterol(TC)in Micropterus salmoides(P<0.05).Compared with the 1.5%and the 4.5%groups,feeding rates of 2.5%and 3.5%could significantly increase the content of reduced glutathione(GSH)in the liver of Micropterus salmoides,and feeding rate of 2.5%could significantly increase the activity of catalase(CAT)in the liver of Micropterus salmoides(P<0.05).Compared with the 4.5%group,a feeding rate of 2.5%could significantly increase the lysozyme(LZM)activity in the liver of Micropterus salmoides(P<0.05).Feeding rates of 1.5%and 2.5%could significantly increase the activity of superoxide dismutase(SOD)in the liver of Micropterus salmoides(P<0.05),and feeding rates of 1.5%,2.5%,and 3.5%could significantly reduce the content of malondialdehyde(MDA)in the liver of Micropterus salmoides(P<0.05).Compared with the 1.5%and 2.5%groups,the feeding rates of 3.5%and 4.5%could significantly increase the long diameter,short diameter,nucleus diameter and vacuolar area ratio of hepatocytes of Micropterus salmoides,and significantly reduce the nucleus area ratio(P<0.05).Compared with the 1.5%group,feeding rates of 3.5%and 4.5%could significantly reduce the number of nuclei in hepatocytes of Micropterus salmoides(P<0.05).Liver tissue sections showed that as the feeding rate increased,the fat accumulation in the liver of Micropterus salmoides gradually increased.When the feeding rate reached 4.5%,liver cell swelling and fat vacuolation were more severe.Studies have shown that a feeding rate of 2.5%to 3.5%helps enhance the antioxidant capacity and immune function of Micropterus salmoides,as well as maintain the integrity of liver tissue structure.